Ted East is the ideal guide for a tour of Inspector Morse's Oxford. A policeman in the city for 26 years, he retired as a superintendent in 1977, then spent 15 years as Marshal of the University, which acts as the backdrop to so many of the television detective's cases.

'I wouldn't say the series rings true,' he said, as I joined a group of Dutch Morse fans on a Saturday morning tour. 'In a real police force he wouldn't last more than a week, upsetting his staff the way he does. But it's good entertainment.'

The tour began at the Martyrs' Memorial, a few steps from St John's College in St Giles' street - founded in 1555 although its gatehouse dates from 1437. It was, Ted told us, the college that Morse attended for 18 months until he left, without graduating, because of an unhappy love affair. Soon afterwards he joined the police, perhaps at the suggestion of his father, a taxi driver.

Opposite the college is the first of the many Oxford pubs that appears in the series - the quaint Eagle and Child, known locally as the Bird and Baby. Morse is a connoisseur of ale. Other city pubs where he is seen quenching his thirst include the King's Arms on the corner of Holywell Street and Parks Road, and the White Horse on Broad Street.

Ted was careful to differentiate in his commentary between fact, the real history of Oxford and its colleges, and fiction, the Morse connections. He led the group back past the stately old Randolph, the city's main hotel, where (fiction) an American tourist was murdered in Room 310 in The Jewel That Was Ours. The plot concerned a jewel destined for the Ashmolean Museum, which is across Beaumont Street from the hotel.

We passed Gilbert Scott's St Mary Magdalen Church, on the island in the middle of Broad Street. This Victorian Gothic church was featured as St Frideswide's in Servants of All The Dead, when two men fell from its high tower. Then we turned into Broad Street for a look at Trinity College - founded in the same year as St John's - whose dining hall was used in the last story of the Morse series, The Twilight of the Gods.

Next door is Blackwell's bookshop, where Morse often browses and where he bought books on Zen Buddhism to assist his inquiries in Deceived By Flight. We crossed the road to look at the Sheldonian Theatre and Clarendon Quadrangle, scene (fact) of a traditional procession for recipients of honorary degrees, during which (fiction) the opera singer was shot in The Twilight of the Gods. Before that untoward incident, she had performed in the Holywell Music Room in Holywell street, built in 1742 and perhaps Europe's first purpose-built concert hall.

Ted took us into the 17th-century chapel of Wadham College, where he explained that 'religion played no part in Morse's life'. Then we went back down Catte Street to the Bodleian Library - built in 1602 and containing nearly 5 million books - and the Radcliffe Camera (1748), featured in several stories. Beyond is Brasenose College, which masqueraded as Lonsdale College in The Riddle of the Third Mile. In The Twilight of the Gods a party was supposed to be held in the college garden, but it was raining on the day of filming, so it was switched to the 17th-century hall of Oriel College (founded 1326).

Ted seemed to be telling us a lot about that particular Morse episode and I wondered why. 'I was in it,' he explained bashfully. 'I was one of the proctors.' The Dutch, who are still seeing some of the programmes for the first time, promised to look out for him.

The two-hour tour ended where it had begun, at the Martyrs' Memorial. But the Morse tourist trail doesn't end there. It including coach trips to sites in the surrounding villages where scenes in the series have been filmed.

One of the most pleasing of them is Thrupp, a village on the Oxford Canal, six miles north of the city. To get there you pass the home of Colin Dexter, author of the Morse books, and the headquarters of the Thames Valley Police at Kidlington, although this is not the building that Morse uses as his base in the TV series.

Thrupp was where a limbless body was dredged up in The Riddle of the Third Mile. Morse was so sickened by the sight of it that he slipped into the Boat Inn, alongside the canal, for a stiff whisky. Real-life visitors will enjoy a short walk along the canal, down to the basin with its colourful narrow boats and an unusual manually-operated swing bridge. The Boat is one of several waterside pubs where Morse pilgrims might want to stop for lunch. Another is the more famous Trout, by the Thames at Wolvercote. It is superb for outdoor eating and drinking on a fine summer's day, as Morse and Sergeant Lewis have found more than once.

The coach tour visits Jericho, an early 19th-century suburb just south of the city, for a glimpse of the row of houses where murders were committed in The Dead of Jericho. The Bookbinders' Arms pub also featured in that story: it gets its name (fact) from the huge Oxford University Press print works nearby.

Woodstock, the village standing just outside the gates of Blenheim Palace, where Winston Churchill was born, is a reminder of Last Bus to Woodstock, and on the coach tour you are shown the very bus stop where the murder victim waited. Two more famous pubs, the Bear and the Marlborough Arms, are also on the route here.

Sampling every tavern featured in the series would be a pub crawl on a monumental scale. Do not try it if you are driving: it could be a costly mistake to assume from watching Inspector Morse that the Oxford police spend all their time getting ratty with each other and listening to Schubert.

Morse tours of Oxford are run by British Heritage Tours of Chester (0244 342222), which also runs Morse weekends and coach trips.

(Photograph omitted)